Questions tagged [integer]
For challenges involving the manipulation of integers.
336
questions
28
votes
44answers
2k views
Multiply or Divide by n
Here's a simple challenge, so hopefully lots of languages will be able to participate.
Given a positive integer \$n\$, output \$A076039(n)\$ from the OEIS.
That is, start with \$a(1)=1\$. Then for \$n&...
33
votes
22answers
3k views
Narcissistic loop lengths
A narcissistic number is a natural number which is equal to the sum of its digits when each digit is taken to the power of the number digits. For example \$8208 = 8^4 + 2^4 + 0^4 + 8^4\$, so is ...
11
votes
13answers
814 views
Prefix divisibility
Inspiration
Given a positive integer \$1 \le n \le 9\$, output all positive \$n\$-digit integers \$i\$ for which the following is true:
Each digit from \$1\$ to \$n\$ appears exactly once in \$i\$. ...
25
votes
29answers
2k views
Not so triangular numbers
Let's consider the sequence \$S\$ consisting of one \$1\$ and one \$0\$, followed by two \$1\$'s and two \$0\$'s, and so on:
$$1,0,1,1,0,0,1,1,1,0,0,0,1,1,1,1,0,0,0,0,...$$
(This is A118175: Binary ...
18
votes
16answers
2k views
A Portuguese sequence of integers
Context
Consider the following sequence of integers:
$$2, 10, 12, 16, 17, 18, 19, ...$$
Can you guess the next term? Well, it is \$200\$. What about the next? It is \$201\$... In case it hasn't become ...
14
votes
23answers
2k views
We're all unique in our own way
This is an answer-chaining challenge where every part of your answer should aim to be unique from every other answer.
This question will work in the following way:
I will post the first answer. The ...
20
votes
42answers
3k views
Converting Strings to Decimals (Gone Wrong)
What?
Many programming languages, both practical and esoteric, have functions, methods, etc to convert a given string to a decimal number. This is how the process might work:
For each character in ...
18
votes
13answers
1k views
Find all integer pairs that produce a given Loeschian number
Inspired by and drawns from Is this number Loeschian?
A positive integer \$k\$ is a Loeschian number if
\$k\$ can be expressed as \$i^2 + j^2 + i\times j\$ for \$i\$, \$j\$ integers.
For example, ...
14
votes
4answers
415 views
Bad matrix multiplication that gives the right answer
Executive summary:
Print NxN matrices \$A\$ and \$B\$ where \$ AB = 10A + B \$. Largest N wins!
Details:
Entrants in this challenge should choose an N. Submit a program that takes an input integer '...
11
votes
1answer
384 views
Amount Of Potential Keys That'll Fit The Lock
Introduction:
You're a key maker, and want to access something from a safe that has a lock. Unfortunately, the key to that lock is lost, so you'll have to make a new one. You have access to a bunch of ...
25
votes
17answers
3k views
A long long time ago, in a galaxy … right here
Task
Given a positive integer return the geologic era and period it was that many million years ago.
Input/output
The input is a string or integer; the output is a string. Eras and periods are ...
19
votes
16answers
2k views
Find the discrete logarithm
Task
Write a program/function that when given 3 positive integers \$a, b\$ and \$m\$ as input outputs a positive integer \$x\$ such that \$a^x\equiv b\ (\text{mod}\ m)\$ or that no such \$x\$ exists.
...
5
votes
5answers
223 views
Divide into 2 isosceles triangles
Given the measures of two of the interior angles of a triangle (x and y; the other angle can be easily calculated with ...
21
votes
6answers
2k views
The matrix has U
Given a matrix of size at least 3Ć3 formed by positive integers, determine if it contains at least one "U" pattern, defined as
...
12
votes
3answers
704 views
Metagolf the OEIS
We've had Meta Regex Golf and Display OEIS Sequences. Now, it is time for Meta OEIS Golf.
Challenge
Given a sequence of integers, your program/function should output a program/function in the same ...
0
votes
2answers
185 views
Remove each integer from a string and multiply them all! [closed]
Goal:
Get every integer from the string (not a number, but integer)
Multiply them
Output the result
Input:
5 kilograms of food eaten, 10 liters of water drank, 20 plates dirty, 40 mugs dirty, and ...
22
votes
23answers
1k views
Complete a sequence using its distances
Given \$A = (a_1,\dots,a_k)\ k\ge2 \$ a sequence of positive integers, in which all elements are different.
Starting from \$i=2\$, while \$a_i\in A:\$ (until the last element)
If \$d=|a_i-a_{i-1}|\$ ...
19
votes
22answers
2k views
Zero the byte (eventually)
Given an infinite arithmetically-progressiveĀ¹ sequence, compute the minimum length of a prefix with a product divisible by 2^8.
Sample cases & reference implementation
Here is a reference ...
12
votes
10answers
2k views
Integers in cosine
Integers in cosine
From trigonometry we know that
\$\sin(a) =-\cos(a + \frac{(4*m + 1)\pi}{2})\$
where \$a\$ is an angle and \$m\in\mathbb{Z}\$ (integer).
The task
For an input of a positive integer \$...
9
votes
8answers
642 views
Perfect scores in Martian rules football
Story
Martians have been observing Aussie rules football matches from space with great curiosity. Having totally fallen in love with the game, they have been inspired to start their very own football ...
20
votes
14answers
2k views
Donation arms race
The barfoos, a hypothetical alien species, go about charity in an interesting way.
Every morning, barfoo Specialists come up with an ordered list of causes to donate to, and for each cause they ...
17
votes
9answers
2k views
Missile-mounted cameras
You are employed as Administrator in charge of Road Maintenance and Planning. The intelligence division of the Agency for Road Maintenance and Planning has come up with a brilliant and not at all ...
16
votes
42answers
2k views
Generate list of numbers and their negative counterparts
A recent SO question asks for a convenient one-liner to generate a list of numbers and their negative counterparts in Python.
Given two integers \$1ā¤aā¤b\$, generate all the integers \$x\$ such that \$...
17
votes
5answers
896 views
Generate Green Spray Paint Patterns
This challenge is about creating these neat "green spray paint" patterns: (more pictures below)
Loosely explained, they are generated by starting with a black image and a point in the center. ...
50
votes
31answers
7k views
Conway's Monster
This challenge is in honor of mathematician John Conway who passed away April 11, 2020 due to COVID-19. He was famous for coming up with the Game of Life cellular automaton and many other mathematical ...
17
votes
3answers
676 views
Make a rectangle from a collection of (sliced) squares
Inspired by Make a Rectangle from a Triangle.
Task
There is a famous formula on the sum of first \$n\$ squares:
$$
1^2 + 2^2 + \dots + n^2 = \frac{n(n+1)(2n+1)}{6}
$$
It is known that this number ...
21
votes
17answers
3k views
Make a Rectangle from a Triangle
You can depict a triangular number, T(N), by writing one 1 on a line, then two 2's on the line below, then three 3's on the line below that, and so on until N N's. You end up with a triangle of T(N) ...
24
votes
9answers
841 views
Maintain diagonal symmetry when placing N items on a square grid
Write a program that takes in two non-negative integers S and N in that order. S represents the side length of a square grid of . characters. N represents the ...
15
votes
14answers
1k views
Generating generating expressions for sequences
(yes, "generating generating" in the title is correct :) )
Context
In middle (?) school we are taught about sequences and, in particular, we are taught about linear sequences where the ...
25
votes
21answers
2k views
Four distinct 8-bit integers
Submit a well-formed program or function with usual I/O rules which satisfy the input, output, and algorithm conditions below. Shortest submission (in bytes) wins. As always, standard loopholes are ...
12
votes
4answers
438 views
Solving the water bucket riddle!
Context
The water buckets riddle or the water jugs riddle is a simple riddle that can be enunciated in a rather general form as:
Given \$n > 0\$ positive integers \$a_1, a_2, \cdots, a_n\$ ...
19
votes
24answers
2k views
17
votes
20answers
2k views
All aboard the factorial train
The system
Assume the Earth is flat and that it extends infinitely in all directions. Now assume we have one infinitely long train railway and n trains in that ...
29
votes
46answers
5k views
How many petals around the rose
How many petals around the rose
How many petals around the rose is a dice game you can play with your friends. Similar to "can I join the music box", there is a person that knows how the ...
15
votes
23answers
2k views
Summing a sub-square of a quarter of an infinite chessboard
Description of the problem
Imagine a quarter of an infinite chessboard, as in a square grid, extending up and right, so that you can see the lower left corner. Place a 0 in there. Now for every other ...
9
votes
5answers
493 views
Computing a specific coefficient in a quotient of polynomials
Context
After "Computing a specific coefficient in a product of polynomials", asking you to compute a specific coefficient of polynomial multiplication, I wish to create a "mirror" challenge, asking ...
34
votes
45answers
3k views
(RGS 1/5) Binary multiples
A binary multiple of a positive integer k is a positive integer n such that n is written ...
38
votes
13answers
3k views
2
votes
5answers
173 views
Shift the digits [closed]
Here, x (supplied as input) and n (the result of your computation) are both positive integers. n * x = n shifted. Find n.
Here's an example of shifting:
...
12
votes
9answers
1k views
Integer Logarithm
Objective
Take \$a \in ā¤_{>1}\$ and \$b \in ā¤_+\$ as inputs. Write a function \$f\$ such that:
$$
f(a,b) =
\left\{
\begin{array}{ll}
\log_ab & \quad \text{if} \space \log_ab \in ā \\...
37
votes
38answers
8k views
Is this a triangle?
Task
Write a function/program that, given three positive integers a, b and c, prints a ...
25
votes
25answers
2k views
Mountain range numbers
Mountain range number
A number is a mountain range number if the inequalities satisfied by their consecutive digits alternate. In a way, looking at the number's digits should exhibit a ...
21
votes
25answers
2k views
Power-Ending Patterns
When you look at the last decimal digit of each power of a non-negative integer a repeating pattern forms. For example, 3:
...
15
votes
16answers
2k views
Computing a specific coefficient in a product of polynomials
Generator functions
This gives the context for why this challenge came to life. Feel free to ignore.
Generator functions are a nice way of encoding the solution to a problem of combinatorics. You ...
33
votes
5answers
2k views
Make The Finest Magic Code Square
In math a magic square is an N×N grid of numbers from 1 to N2 such that every row, column, and diagonal sums to the same total. For example here's a 3×3 magic square:
In this challenge we'...
5
votes
15answers
3k views
Move my liquid to make me equal
You are given 4 positive integers: volume of the first container (v1), volume of the second container (v2), volume of the liquid ...
20
votes
9answers
2k views
Proportion of self-avoiding walks on a square lattice
The challenge
Given a positive integer N, compute the proportion of N-step walks on a plane that don't intersect themselves.
...
22
votes
40answers
4k views
Round up my number
Sandbox
Given two positive integers a and b, return the smallest multiple of b that is greater than or equal to a.
Examples
Definitions: true = ...
16
votes
16answers
1k views
Find the length of a number's “base-jumping” path
Consider a positive integer N written in base b. A sequence is generated from this number by finding the largest digit ...
25
votes
7answers
2k views
Inverse Look-and-Say
Background
The Look and Say Sequence is built up by reading off the digits of previous entries in the sequence, counting the number of digits in groups of the same digit. For example:
...
